Attachment for chasing threads on horizontal lathes



June 22, 1965 P. clccARELLl 3,190,157

'ATTACHMENT FOR CHASING THREADS 0N HORIZONTAL LATHES Original Filed April 6, 1956 INVENT OR.

PIETRO CICCARELLI United States Patentfo.

This application is a division of my corresponding applicaton Serial Number.576,565,iii1ed April 6, 1956,'n0w Patent No. 3,073,194 issuedJanuary 15, 1963, and is V.directed more speciiically to the construction shown on FIGURES 4, 5 and 6 of the parent application.

It is the chief object of the invention to provide a thread-chasing attachment which may be applied to exist ing lathes equipped with a feed screw and which, once adjusted for any particular `set-up, will operate semiautomatically, andwith a minimum of attention to complete the threads of `each individual workpiece.

Another object is to provide in a thread-chasing attachment of the type mentioned, a cross-feed for the tool which operates to condition and determine the amount or distance of advance of the tool toward the work by and in responseto movement of the longitudinal slide and the tool carrier into linal position during each working roke.

A still further object is to `provide a chasing attachment las inthe preceeding paragraph wherein the actual advance of the tool toward the workpiece, or the axis rotation thereof is effected by means which become operative ,on initial movement of the slide and carrier in the retro- 'i grade or`return direction of translation parallel with the axis of rotation of the Work.

Yet another object is to Aprovide a thread-chasing attachment which makes' it possible .to vary, in a simple way, the distance of advanceY of the tool toward the work, for each stroke ot the longitudinal slide.' n

Another object is to provide a thread-chasing attach ment as aforementioned, wherein the tool is automatically rendered incapable of further cutting by and in response `to completion of the threads' to a preset or predetermined depth or in other words, to a pre-set maximum ad- `vance1of the tool toward or into the workpiece.

StillA another object is to provide a, thread-chasing attachment'which is quickly, easilys,urely and accurately reset for operation upon the next workpiece, after completion of the previous one.

Another object is to `provide an attachment ofthe nature disclosed, which is 'relativelyV simple and inexpensive to produce, reliable and accurate in use, quicklyattached to and adjusted for use in connection with an existing lathe `equipped Awitha feedk screw, and versatile over a wide range of conditions of use. Y

Other objects and advantages ofthe invention will l become obvious toithose skilled in the art,after a study of the following detailed description, in connection with the accompanying drawing. t In the drawing:

FIGURE 1 `is`a vertical longitudinall section taken g1 va pla-ne identified by the line I-I'of FIGURE 3;

FIGUREZ is an elevational view of theassemblyv of 1FIGURE l, the -front wall of the enclosureffor the mechanism ,feeding the tool carrier toward the workpiece being removed; Y

n, FIGURE 3 is a plan View `of the attachmentparts being broken away to moreV clearlydisclose important features;

FIGURE 4 is a `detail view, partly broken away, showing the invention;V

FIGURE 5 is aV section taken in a plane. identified by `fline 5 5 of FIGURE 6; and

ice

FIGURE 6 is a top plan detail of the manual adjusting means for the depth of cut. Y

Referring in detail to the drawing, 1 identifies one end of a telescopic transmission shaft, connected by a universal joint 1a to rotatey a worm, notl shown, in mesh with a gear 2 forming a part of the invention. The other end of shaft y1 `is connected to be driven by andfrorn` the feed shaft of a lathe, as'shown and described in British Patent 764,926, so that gear 2 is rotated in timed relation therewith.

The base or frame of the attachment is identified as 1b, FIGURES land 2 and is adapted for iixedly mounting upon the bed or the carriage ofa lathe ofconventional construction. Gear 2 is keyed to a vertical shaft 3 jour- `naled by antifriction bearing 1c and 1d for rotation aboutv a verticalV axis in base 1b. The upper end of the shaft protrudes into the casing and has a specially shaped and constructed cam 4 removably xed to its upper end as by cap screw 4b. Y

A slide 6 is mounted upon base 1b for guided horizontal translation in a direction which in normal operation, is parallel with the axis of rotation of a workpiece mounted between lathe centers. A roller or cam follower 5 is journaled on slide -6 for engagement with the periphery of cam 4 so that, in a manner clear from inspection of FIGURE 3, the slide is translated leftwardly, as viewed in this gure, by and in response to rotation of the cam in the direction of the arrown A transverse carriage or tool carrier 7 is mounted upon slide 6 for guided movement in a second direction perpendicular to the direction'of translation of slide 6 upon base 1b. In normal operation, this second direction is toward and from the axis of rotation of the workpiece.`

Referring especially to FIGURES 1 and 3, a bar 9 is mounted in guideways 9a xed to the under side of slide 6, for translationrelatively to the slide in the direction parallel with the direction of movement of slide 6 upon base 1b. At its right end as seen upon FIGURES 1 and. 3, this bar carries a roller :8 adapted to be periodically engaged by a portion 4u of cam 4, as subsequently described. It should be particularly noted upon FIG. 3, that roller 5 is not journaled on bar 9 but is pivoted to the under side of slide 6. The ,left end of bar 9 is formed with an` upwardly-facing channel 9b which, as clearly as` shown upon FIGURE 3, extends at an angle, both to the direction -of movement of slide 6 `upon base 1b and of, carrier 7 upon and relatively to the slide. Carrier 7 is provided with pin 1'1. A follower 10 isV journaled for rotation upon the lower end of this pin and has a smooth llit within channel 9b so that, as bar 9 is translated relatively to slide 6, carrier 7 is correspondingly moved relatively to the slide, that is, toward and from the axis of rotation of the workpiece mounted between centers in the lathe. A coil spring 12, FIGURES 1 and 3, is mounted within a channel or recess in the under side of slide 6 and engages the left end of the recess. At its right end the spring engages an abutment 9c xed with bar 9, to thus tivelysrnallangle of rotation of the cam, so that roller 8,

previously identiied, is positioned on bar 9 in the... plane of rotation of cam position `4ato vbe engaged'- thereby substantially at the instant the greatest radialdim'ension of cam 4 is eective upon follower 5, or, in'other words, at the instant slide 6 reaches its extreme leftward position jduring'the working stroke. K Y Y Y Vthereby shifted leftwardly a short distanceY relatively t continuously; urged to the translation,

. by reciprocations ofV plunger 34, FIG. 4.

At this `instant the .bar 9 is slide 6, and, due to the action of channel 9b on block .10, Ycarriage 7 is retracted from the workpiece toV withdraw therefrom a tool, not shownmounted upon thecarriage.'Y

YBy theV construction just described, the slide 6, carriage i 7 and tool, are translated by cam 4in the directionparallel, with the ,axis Vof rotation ofr the` vworkpiece in a'worlung stroke, and intimed-relation with Ysuch rotation.Y 'The numerical Value of such timed relation will, :of course, de'- pend uponthe; pitch of VtherthreadsbeingY cut and is varied by the change gears ofthe lathe itself. VAt theend Y of the working stroke, portion Aa'engages roller S and acts positively to Vretract the'tool from the work and to Y maintain Vit retractedfuntiljthe slide has completedY its 'v 'retrograde ork return movement. Y

This' return movement isY eected Vby a pair of identical andthe other of which 13, is shown'uponFIGURErZ. Each springtsurrounds ya respective one of .two Vreds* 6.a

- and 6b fixed in the right end of slide` 6 and against which thersprings abut at their right.; ends. Therother or left e1r1ds of.the A springsabut base 1b, so .that'uthe slide 1s The meansfor automatically advancing the tool into the work by predetermined incrementsis shown upon FIG- URES 4, 5 and 6V. In'theV embodiment shown, the carrier 7 hasV an extension Y7:1,7F'IVGURES 5 and 6. A shaftt33 `is journaled in this extension, for rotation uponla horizontal axis parallel withjthedirectionrof translation of carrier l '7 on'and relatively to slide 6. VA combined ratchet wheel andY cam element 30 is fixedtoftheinner or forward end of the shaft. nThe cam is identified at 39a and comprises `a surface in the form of ahelix aboutrthe axiszof rotation of the shaft. VAt its yforward Vend 'this helical; surfaceA Vterminates)abruptly in an endsurface, or shoulderdis-v posed substantially in a radial plane through the axis of shaft 33 and Vextends from the shoulder at a constant helix v angle or pitch to a point about 360 from the shoulder, at K which point the Vsurface merges smoothly intorthe kcontiguous face ofthe ratchet Wheel. The'exposedouter'or rearward'end of the shaftehas a/knurled knob 32 xed thereto, which, as seen upon FiGURE 6 Yis-provided with graduations readable against an index fixed with extension 7a whereby ne measured adjustments or rotations of cam Y -'30a may be effected. The ratchet wheel itself hasteeth extending over a'portion only of its periphery.V The remaining portions'of ,its'periphery is smooth and unaffected ,Thee depth of cut for anyY given work mined by theV angular `rotation of cam 36a for each `stroke or reciprocation of the slide. The amount of.

this'rotation, of course, depends'in any given set-up, upon theadjusted `position of'abutment 38. Thus'carrier '7 and 1 the `tool fixed thereto move toward the work'at the beginning of'eachworking stroke, untilcam 30a engages a l *follower 31 removably ivxedrwithY slide 6;`V Thisfollower is L offset slightly belowshaft 33 so'that turning of the shaft effects a `fine controlledradjustmentrof Vthepcarrier toward f right, that is, inretro'grade,

i Y570 stroke is Ydet'ersmooth guided movement axially jthere'along. Anysuitable means, not shown, are provided for preventing rota- Y tion of the plunger in thepbore.'V The Vmidportionof the plunger is recessed to receive a pawl 3S having one'end pivoted within the'recessrformovement about'an axisV 1 normal Vto the axis of the bore. YA leaf spring interposed t between the recess and pawlurgesthe other end thereof intoV engagement with ratchet wheel 30. The kupper-'end Y or right end of bore 6c, as'seenlu'pon FIGURE 4, is closed `VV10 by a plug 37. A coil fspring'36 housed inthe bore, acts between the plugV and plunger tol urge the latterftoward "coil springs, one ofwhich 13a is shown at FIGURE l Y the Yaxis ofrot'ationeofthe workpiece.y TheA follower has j a short section of helicoidal'surface formed at the same helix angle V.as thatof cam-36a, so 'thatthe two are in Contact 'over a substantial areaY to reduce .pressure and f wear.A The graduationson knob32 may Abier-in terms of 'the linear distances of advance Y.of ycarrier '7 towardY andfrom the axis of rotation of the workpiece.;

The lower `or left end of the-plunger is reduced, as Y. shown at 34a to form a shouldenwhichengages theleft "end of the bore Yto thuslimit the movement` of the plunger n in'. Vthis 'directiong The `reduced end of the Yplunger is` Y, positioned to engage an abutment 38 forV limited guided,

Ymovement.horizontally in Vand along `a guide` channel or groove 14) in .brase lbt A Vset screw '39. acts-to fix the abutment in a s electedposition of adjustment in and along Vthe channelf The relative'positions and-relations of .the t Y parts are suchthat thereducedendiaofplunger engages abutment; 38, as slide V6approaches its final left-jV ward position during a Working stroke. The precise point'V of engagement maybe varied by a.'correspendingV adjustment of theabutment.` 0n engagement of the plunger with the abutment, further leftward movernentofV slide 6 causes" the plunger' to move to the Vright relatively to the slide, so that, thepawl k35 rides Vfreely overa predetermined ordesired number ofthe teeth of ratchet wheel 30 and `of course, withoutrotating Vthe`wheel. Atthe Y instantV the'Y slide Vrnovesinto Vfinal position, cam l.portion 4rz`actsrto retract carriageV 'i and the tool mounted lthereon, as wellras camVY 36a from the follower 31.it will `be 'understood that the `surface of abutment "'38 engaged` by thefend 34:; of plunger 34, has a dimension in a planenormal to the plane iof FIG. 4 so that end 34a V'will engage Vthe surface'for the limited range ofV movement of V.carrier ,7,7 on .and relativeto slide V6. i

VrelationV with ,Y rotation l,of the ,e workpiece, Ypermits Yinitivation of return orretrograde movementof the `slideV under urge of springs 13a, spring V36, acts upon plunger T34'V to moveV the sameoto the Vleft relatively toV slideV As a result pawl 35 jreffects clockwise i 'rotatioh `issuficientto Vrotate vshaftf33.f' ,r It has been explained 4that 'ratchet in an'obvious way, the scale on'knob`32 may be directly Carrier 7 Yhas Va bore 6c the axis of which'lies in a vertical .i

Y'planenorrnal to the direction of its inovementonslide 6 and is inclined in said plane downwardly'andfto the Y left, as appears from inspection o f VFIGURE 4. It shouldu be added that theV aforesaid"verticalplne also contains the ratchet wheel 30. 'Y

e A plunger 34 is mounted Wittenberg' 6C FIG. 4, fdr

YVcenters, the "operatorf adjustsV abutment 38 to 'a' position s A which'` willrgive the desired" advance ofthe tfoolgintoY the f Ywork foreach stroke of thcfslide. YYTheadvairce.will, 'ofc Y course, depend upon the `materiali ofthe workpiece', the;

in terms of -the depth of thread"tobejcutihr Y VThe operation will be clearfrom thejforegoingdescrip-f 'tion,1and is resumed as follows:

r`Base 1a; is fixed VVto the lathe; crossjslide',iin, position such that slide 6` moves parallel `withtl1eaxis ofrotation o f the work and carriage7 movestoward and from the i axis; within@ part to be threaded Vmf'mnted between 15th@ As soon as cam-*4,1m itscontinued rotation `in timed Y wheel-30whasa Y portion of itsperiphery blank Vor, smooth soV that` pawl 35 is ineffective thereon. jfA'satisfactory relation Yissuch '1 that thissrnooth portion is `presented to pawl YV35 'co4' incident with the `rotational position of"helicoidal sur` face 3mi enabling 'maximumvadvance .of 'carrier'.v? toward V the axis ofV rotation ofY therworkpiece. f yThus t tions of equivalents will be obvious.

slide 6 is in its extreme leftward position, Vso that plunger `34 is in its limiting position to the right within bore 6c and the lathe carriage is` adjusted until the tool on carriage 7 is at the left end'oftheV portion of the workpiece to be threaded. The change gears of the lathe are then meshed to give the proper, preselected speed ratio between the feed screw and chuck.` This will, of course,

`depend upon the pitch or helix angle of the threads to be cut. Cam 30a is adjusted, `by rotation offknob 32,- until the. cam follower 31 rests on `a certain portion of the helicoidal surface of the cam.` This position of adjustment is such that, on continued rotation of the cam, the tool will have been let into the work by a distance equal to the depth of the threads to be cut, at the instant the smooth or toothless portion of ratchet wheel 30 moves into contact with pawl 35, and is readily determined by the graduated scale of knob 32. .With the lathe cross slide adjusted so that-the tool is out of contact with the workpiece, the lathe is operated to bring slide 6 to its extreme right position, ready to start a work stroke. The lathe slides are-adjusted to bring the tool into contact with the Workesurface to Vbe threaded at the right end of the surface to be threaded. Y Knob 32 is adjusted for the depth of the rst cut. The feed screw is connected with the powerfdrive'and the motor Yis started. As slide 6 approaches its nal position in a work stroke, end 34a o'f plunger 34 is engaged byabutment 38 and moved against the urge of spring 36 by a distance and over a number of teeth on ratchet wheel 30a, predetermined by the preliminary adjustment of the abutment, as described. At the instant carriage 7 arrives at the end of its Vcutting or working stroke, it is retracted by cam portion 4a. Thereafter, as slide 6 begins its retrograde translation under the thrust of springs 13 and 13a, plunger` 34 moves to the left in and along its bore, and cam 30a is rotated so that when carrier 7 is released by cam surface 4a, it is moved by spring 12 to advance the carrier and tool xed thereto by the predetermined distance before the cam engages follower 31. i

At the instant the slide has completed its retrograde translation, cam portion 4a rides oif roller 8 and the tool is advanced into the work to make a new cu-t. The cycle is then repeated. At the instant that theV thread has been completed to the desired depth, the smooth or toothless portion of the periphery of Wheel 30 is presented to pawl 35 so that the latter is ineffective to further rotate the wheel. Consequently, no damage to the work can occur by letting the slide make one or more additional strokes.

As soon as the thread has been thuscompleted, the workpiece is replaced by another, knob 32 is reset, and the lathe is again set in operation. 'I'hus the operation once started is completed automatically andthe operator is not required to give constant attention thereto. When the thread is completed, further cutting ceases even although the slide continues to reciprocate under rotationv of cam 4.

Many other Ways of utilizing the invention will be ob vious to those skilled in the art, after' a study of the foregoing description. Likewise, modication and substitu- Therefor, the description should be taken in an illustrative rather than a hunting sense.

Having thus fully disclosed the invention what I claim is:

1. In a threading attachment for a lathe adapted, to mount and rotate a workpiece about the conventional axis ofrotation of a lathe, a base, a slide mounted on said base for guided translation in a first path, a tool carrier mounted on said slide for guided translation in a second path toward and 'om said first path, a helicoidal cam `journaled .on said carrier for rotation about an axis parallel with said second path,`and engaging said slide, rotation of said cam effecting advance of said carrier transversely of said first path, a ratchet-wheel fixed with Vsaid cam, pawl means carried by said slide for translation with respectthereto, and engaging said' ratchet Wheel, an abutment xed with said base and, in response to translation of said slide, moving said 'pawl means in one direction to pass freely over said ratchet wheelwith- 'out rotating the same, and spring means engaging and urg- `a second path toward and from said first path, a helicoidal cam journaled on said, carrier for rotation about an axis parallel with said Vsecond path and rotatably engaging said slide, said cam being rotatable to effect movement of said carrier transversely of said first. path, anabutment iixed with said base, a plungerv movably carried by said slide, spring means urging said plungergin one direction of movement, said plunger engaging. andl being moved by said abutment, against the urge of said spring means, as said slide moves into final position in a working stroke, ratchet and pawl means between'said plunger and said cam and operable to rotate the latter under urge of said spring means as said slide recedes from said abutment in retrograde translation, and means translating said slide in working and retrograde movements.

3. In a threading attachment for a lathe adapted to mount and rotate a workpiece about'the conventional axis of rotation of a lathe, a base, a slide mounted on said base for guided reciprocation in a first path, a tool carrier mounted on said slide for guided transulation in a second path, toward and from said first axis, and springurged toward said first path a unitary ratchet wheel and cam element journaled on said carrier'for rotation about an axis parallel with said second path and engaging said slide, rotation of said cam permitting and controlling advance of said carrier along said second path, a plungen mounted on said slide for reciprocation in a plane normal to said second path, spring means urging said plunger in the direction corresponding to translation of said slide in vrecedes from said abutment in a retrograde stroke, and

means reciprocating said slide in timed relation with rotation Iof said workpiece.

4. A threading attachment as in claim 3,V said abutment being mounted to said base for adjustment in and along said first path, and means releasably, fixing said abutment to said base in adjusted position to correspondingly vary the stroke of said plunger.

5. In a threading attachment for a lathe adapted to mount and rotate a workpiece about the conventional axis of rotation of a lathe, a base, a slide carried by said base for guided translation in alternatework'and retrograde strokes in a first path rst spring means urging said slide in retrograde movement, earn means journaled on said base and rotatable to engage and move said slide in working strokes, a tool carrier mounted on said slide for guided translation in a second path toward and from said first path, a unitary helicoidal cam'and ratchet wheel journaled on said carrier for rotation on an axis parallel with said second path, and engaging said slide,.said cam being rotatable to permit advance of said carrier parallel with said second path, pawl means carried by said slide and engageable with said ratchet Wheel to rotate the same only Yin response to retrogradeV movement of said slide `on andi relatively to said base,'and abutmentmcarried by vsaid base for adjustment in and along s aidv first` path, said pawl means engagingsaid abutment, to be moved Ythere- Y Y by, as said slide approaches the terminus ,ofY its working stroke, and second Yspring means urging-saidkpawl means in said carrier parallel with said'rsecond pathrarcam lixed with said; shaft and havingfa helicoidal surface coaxially into movement rotatingsaid ratchet Wheel, as said slide recedes 'fromsaid abutment invvretrograde motion.

6.` An attachment as in claimjS, there being a Abore-irl -isaid slide with axis in a planernormal to said second ipath, `said pawl means comprising a plungerwslidaoly fitting Asaid I bore, said second spring means engaging 'and urging said plunger in one direction in and alongsaid bore, a'pawl pivoted to said plunger,V and a spring urging said'p'awl into j Y engagement with said rachet wheel. Y'

7. An attachment as in claim 5, abarcarried by said slidefor guided movement in said first path, a connection between said bar and said carrier and operable to retract said carriersfromsaid rstaxis by andin response to onedirectionof movement of said bar relatively/toY said slide, saidv cam means engaging and moving said bar as said sliderapproaches the terminus kof its workingstroke kto retract said carrier as aforesaid, said cam means rethereof, a ratchet Vwheel ,having successive smooth and toothed peripheral portions and-fixed with saidam,` a

f, cam follower fixed with `said slide; spring means urging Y said carrier toward said irst path to maintain said heli-` {coidal cam surface in contact withsaid followerfpawl means-carried byV said 'Vslide'for reciprocationv in arplane 1 ,normal to said second Vpath and Vengaging `said fratchet Y ,Y

YWheel to rotate thesarne Y,onlyin-presponse to, retrograde :translation'ofsaid slidetvffr l 1 9.. An attachment aslin clairnS, anahutment adjustable y when the t wheel presents leasingvsaid bar as said Slide Vbegins a succeeding working K stroke, .and Vmeans yieldingly urging said bar in its other kdirection ofk movement on and relatively. to Ysaidrslide 8. In a lthreading attachment for azlathefadaptedto "lon said base parallel with said .first pathand `positioned to beengaged 'and reciprocate said pawl means VVas Vsaid"v slide approachesits inal position in a work strokeysaid y ,Y

pawl means becoming inetlfectivexon saidVV ratchet wheel wnLIAM W. DYER, Ja., Primm Examiner'.

4itssrn'ooth peripheral portion` 

1. IN A THREADING ATTACHMENT FOR A LATHE ADAPTED TO MOUNT AND ROTATE A WORKPIECE ABOUT THE CONVENTIONAL AXIS OF ROTATION OF A LATHE, A BASE A SLIDE MOUNTED ON SAID BASE FOR GUIDED TRANSLATION IN A FIRST PATH, A TOOL CARRIER MOUNTED ON SAID SLIDE FOR GUIDED TRANSLATION IN A SECOND PATH TOWARD AND FROM SAID FIRST PATH, A HELICOIDAL CAM JOURNALED ON SAID CARRIER FOR ROTATION ABOUT AN AXIS PARALLEL WITH SAID SECOND PATH, AND ENGAGING SAID SLIDE, ROTATION OF SAID CAM EFFECTING ADVANCE OF SAID CARRIER TRANSVERSELY OF SAID FIRST PATH, A RATCHET WHEEL FIXED WITH SAID CAM, PAWL MEANS CARRIED BY SAID SLIDE FOR TRANSLATION WITH RESPECT THERETO, AND ENGAGING SAID RATCHET WHEEL, AN ABUTMENT FIXED WITH SAID BASE AND, IN RESPONSE TO TRANSLATION OF SAID SLIDE, MOVING SAID PAWL MEANS IN ONE DIRECTION TO PASS FREELY OVER SAID RATCHET WHEEL WITH- 